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Wheel Alignment CASTER.

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Presentation on theme: "Wheel Alignment CASTER."— Presentation transcript:

1 Wheel Alignment CASTER



4 Effects of Caster High Positive Caster increases ( + ) Straight ahead stability Steering effort required is high Steering wheel return to center Road Shock felt from bumps More Negative Caster ( -- ) No Straight ahead stability Steering effort is light Wheel not returning to center Smooth ride, little road shock Uneven Caster will cause the vehicle to pull towards the side with less Caster (more Negative -) ½ degree or more Not a tire wearing angle!!!!

5 Caster can be set unevenly to counter act for road crown pull.
Usually ½ degree or more on the downhill side. Caster trail is the distance between the caster line and the tire point of contact.


7 Camber = The inward or out ward tilt of the centerline of the tire.

8 Camber The more camber you have, the more the load is placed on the outside of the tire. Excessive positive or negative camber can cause tire wear on the edges

9 Camber can cause a car to pull to one side

10 Effects of Camber Tire wearing angle Directional control angle
Pull towards the side with more positive camber Excessive Camber Accelerates bearing wear Load is not evenly set on bearings. Positive wears the inner bearing Negative wears the outer bearing

11 Influences on Camber Uneven Loading Body roll during turns Road Crown
Rough road Surfaces Suspension Wear Suspension Damage Tire size Caster Faster cornering wears out edges of tires!!!!

12 Camber can be set unevenly to counter act for road crown pull.
Cross Camber should never exceed ½ degree Camber will pull to the most positive side Camber Roll Caster angle may produce a change in the camber angle when the wheels are turned

13 Camber is adjustable on most vehicles



16 Toe Toe in Toe out



19 Darting Darting

20 Wander

21 Toe Toe in = Darting Toe out = Wander

22 Effects of Toe Tire wear Scuffing sideways Scuffing is Drag and hop! Wear tends to be the same on both tires, unlike Camber wear Directional control angle Can cause shimmy! Diagonal Wipe on the rear tires if toe is excessive Lots of rotations! Toe Change can occur as suspension travels up and down. Measure toe change at 1 inch increments Should be no change! Check length and height of tie rods!!! City driving can cause unusual tire wear that might be blamed on Toe problems!!

23 Steering Axis Inclination
SAI Steering Axis Inclination

24 (looking from the front)
SAI The inward tilt at the top of the strut. (looking from the front)

25 (looking from the front)
SAI The inward tilt at the top of the strut. (looking from the front)

26 SAI and Included angle Include angle = SAI + pos. camber



29 Effects of SAI Ensures Steering stability
FWD use more SAI because of small Caster Helps with Steering Wheel returnability Uses Gravity to assist

30 Diagnosis with SAI SLA & Strut/SLA
Camber Included Angle Diagnosis Correct < spec Bent steering Knuckle < Spec > Spec Bent lower control arm Bent lower arm & Knuckle or spindle Bent upper control arm

31 Diagnosis with SAI Strut Suspensions
Camber IA Diagnosis Correct < spec Bent spindle or strut > Spec Bent control arm or strut >Spec Bent control arm or strut or spindle. strut tower out at top strut tower in at top correct Strut tower in at top And bent spindle & strut

32 0 bump steer Zero SAI would = Major bump steer No toe angle change.
Need to Check for this at 1 inch increments 3 factors affect bump steer Tie rod length Relative heights of inner and outer tie rod ends Steering arm length Zero SAI would = Major bump steer

33 Positive Scrub Radius Positive scrub radius RWD vehicles Sport cars
Feel the steering wheel tug when braking Road feel Driver Involvement needed

34 Negative Scrub radius Used on Split diagonal braking systems
Self Correcting when braking No driver involvement needed No road feel


36 Effects of: Larger tire smaller tire deep dish wheel Larger Scrub = harder to turn and increased wear Smaller Scrub = easy turns Braking stability - Negative has greater directional stability Positive decreases braking stability (aftermarket rims)

37 Turning Angle Setback Thrust Angle.

38 Turning Angle

39 Setback

40 Thrust

41 The End Thanks to Specialty Products Company

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